Manufacture of iron carbonyl



Patented Jan. 1927 UNITED STATES PATENT OFFICE.

MAR-TIN Mfi'LLER-CUNRADI. OF LUDWIGSHAFEN-OAT-THE-RHINE, GERMANY. AS- SIGNOR TO I. G. FARBENINDUS'IRIE AKTIENGESELLSCHAFT, OF FRANKFOBT-ON- THE-MAIN, GERMANY, A CORPORATION OF GERMANY.

MANUFACTURE OF IRON CARBONYL.

No Drawing. Application filed May 27, 1926, Serial N 0. 112,124, and in Germany January 5, 1925.

1a respect of the thermal effect.

\Vhen working in this manner in the manufacture of iron carbonyl by acting with carbon monoxid under pressure on heated iron, considerable troubles have been is observed. Sometimes the temperature would rise all of a sudden by several hundred degrees centigrade whereby not only the desired reaction comes to a standstill, but also great danger is caused, resulting even in a destruction of the apparatus.

I have now found that these drawbacks can be avoided by taking care that at all places where iron carbonyl, even in a dilute state, is present or can be formed, no temperatures occur which are considerably higher than those favorable to the formation of iron carbonyl (which temperatures depend on the pressure employed in each case) as otherwise a decomposition of carbon monoxid connected with a strong evolution of heat may take place, As a rule, the high pressure vessel containing the iron mass should not be superheated more than .by about 50 to 80 C. Accordingly, when for example working under 200 atmospheres and at a temperature of about 200. C. the highest permissible temperature of the walls or the iron mass is about 250 0., while when working at a pressure of 1 atmosphere and consequently at a temperature of as low as about 0., the temperature should not substantially exceed about 100 to 120 C. anywhere.

A greater diiierence of temperatures can be prevented in any known or suitable mannet, for example by employing a source of heat which cannot give use to a higher temperature such as saturated steam of suitable pressure or a heating bath of the desired temperature. However, any source of heat having a higher temperature may also be employed, provided that surpassing of the permissible excess of temperature is prevented in a suitable manner. Regard must also be had to the fact that the combination of carbon monoxid with iron evolves heat and it may be necessary to apply proper cooling or radiation with the walls of the reaction vessel in order to keep the temperature down at the desired level. This may also be ensured by a proper attendance for example by a reliable measurement of temperature with or without connection with an alarm device or with an automatic control of temperature.

These precautions are not only necessary for the reaction vessel, but .also for other parts of the apparatus to be heated, for example the gas preheater in caseheating is efi'ected partly or entirely by preheating the fresh gases prior to their introduction. There the diiierence of temperature may be greater to a certain extent than with the reaction vessel, though it must be considerably lower than would be usual in similar cases. However, when Working in a, circular course and again heating the carbon monoxid in a preheater after; separating the bulk of iron carbonyl from it, the permissible difierence of temperature is smaller than when introducing fresh carbon monoxid. Probably, it is due to the small quantities of iron carbonyl left in the carbon monoxid after separation that in the former case troubles occur more readily than in the latter case.

The following example will further illustrate how my present invention may be carried out in practice, but the invention is not limited to this example.

A reaction vessel in which iron metal is to be acted upon with carbon monoxid under a pressure of about 200 atmospheres is heated by a bath heated to 230 C. or by a steam jacket or coil through which hlgh pressure steam of about 220 C. is passed. The carbon monoxid to be introduced into the vessel is'preheated in a heat exchanger by means of the hot gases leaving the reaction vessel and, if necessary, in a preheater provided with a heating bath or with a coil throu h which high pressure steam is passe as described above. action proceeds with sufficient speed, the heating of the reaction vessel and the gas preheater can be discontinued both at the same time or one after the other. If neces- When the resary, the steam coils and the like may then bonyl is present, an occurrence of tempera- 10 serve for cooling by passing water through tures which are considerably higher than them. those employed for the formation of iron I claim: carbonyl so=as to avoid a decomposition of 6 The process of manufacturing iron carcarbon monoxid' bonyl which consists in acting with carbon In testimony whereof I have hereunto set 15 monoxid on iron under pressure and at an my hand. elevated temperature While avoiding in all parts of the apparatus in which iron car- M RTIN MU L R-'GUNRADI- 

